xProfile: Update Markup and Styles of User > Extended Profile screen

[mercime]

Requires #7348 => currently ​7348.3.patch

Structural changes on the xProfile input types for the front end (e.g. #6678 & #7083) require updates on the back end (e.g. #7080 & #7081).

After grouping related form elements within fieldsets for the Profile > Edit screen in #7348, we need to adjust the markup and styles of the Extended Profile screen on the back end.

Patch and screenshots coming up.

[mercime]

After 7348.3.patch and befre 7439.patch

[mercime]

After 7348.3.patch and after 7439.patch

[mercime]

7439.patch​ provides style support and closing </fieldset>.

[mercime]

7439.2.patch​ adds aria-describedby, aria-expanded, and aria-label attributes to <button>s for parity with front end accessible <button>s.

[mercime]

@hnla per earlier conversation after commits in #7348, 7439.3.patch​ fixes markup and styles accordingly for the wp-admin User > Extended Profile screen. Includes new screenshot 7439-user-extended-profile.png​

[mercime]

In 11620:

xProfile: Update markup and styles for User > Extended Profiles.

After accessibility upgrades for the Profile > Edit screen in #7348, we need to
update the wp-admin Extended Profiles screen as well.

Fixes #7439.

[mercime]

In 11625:

xProfile: Improve mobile view of User > Extended Profile screen.

See #7439.